Mass spectroscopic analysis

Chemical Properties. Vacuum thermal degradation of PTFE results in monomer formation. The degradation is a first-order reaction (82). Mass spectroscopic analysis shows that degradation begins at ca 440°C, peaks at 540°C, and continues until 590°C (83). 

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

An indication of the range of such clusters which might possibly be synthesized is given by the observation that mass spectroscopic analysis of the products of laser-ablation of CoS... 

Various ionization methods were used to bombard phenol-formaldehyde oligomers in mass spectroscopic analysis. The molecular weights of resole resins were calculated using field desorption mass spectroscopy of acetyl-derivatized samples.74 Phenol acetylation was used to enable quantitative characterization of all molecular fractions by increasing the molecular weights in increments of 42. 

Purification of the radioactive tracer was modified to include a fractional sublimation before a single extraction—recrystallization cycle to conserve the tracer material. Microgram samples were prepared in melting point capillaries for assay by mass spectroscopic analysis (Table III), made by direct probe injection of the sample into the ion source (18). The probe was heated rapidly to 200°C, and mass spectra were obtained during vaporization of the sample. Tri-, tetra-, and pentachlorodibenzo-p-dioxins vaporized simultaneously with no observed fractionation. 

The use of mass spectroscopic analyses for characterization of anthocyanins has increased dramatically over the past decade. Most reports cite the use of HPLC coupled to MS detectors or isolating individual pigments prior to the mass spectroscopic analysis. - - " ... 

An inductively coupled plasma formed by passing argon through a quartz torch is widely used for the mass spectroscopic analysis of metal compounds separated by online HPLC.6 Samples are nebulized on introduction into the interface. Plasma impact evaporates solvent, and atomizes and ionizes the analyte. Applications include separation of organoarsenic compounds on ion-pairing F4PLC and vanadium species on cation exchange. 

Comparative Evaluation of Related Compounds. Structural studies are incomplete, but NMR and gas chromatographic - mass spectroscopic analysis of a component (fraction 7) isolated by HPLC indicated biphenyl characteristics (30). In an attempt to evaluate the cytolytic effect of compounds with similar structure, 4-hydroxybiphenol and 2-hydroxybiphenol were tested for lytic effects on P. brevis. Bioassays of 2- and 4-hydroxybiphenol indicated that both compounds were cytolytic to P. brevis (31). 

V.P. Papageorgiou, M.N. Bakola Christianopolou, K.K. Apazidou, E.E. Psarros, Gas chroma tographic mass spectroscopic analysis of the acidic triterpenic fraction of mastic gum, Journal of Chromatography A, 769, 263 273 (1997). 

Mass spectra from HPLC separations are obtained in a manner similar to those from GC-MS. Unlike GC, where both the eluent and analyte are in the gas phase, HPLC eluents are dissolved in liquids that are stripped off before mass spectroscopic analysis is carried out. Analytes must also be vaporized before analysis. For this reason, metals are usually introduced via either AA or ICP As with GC-MS analyses, the mass spectra from each eluted compound can be compared with standards and the compound identified. 

All of the allylniobium compounds are monomeric, as revealed by the mass spectroscopic analysis, and always exist in the thermodynamically more favored syn- or... 

Mass spectroscopic analysis of the gas phase revealed that 53 is formed with the concomitant generation of H2. Based on the proposed catalytic cycle for silyUbrmylation (Scheme 6.12), the formation of 53 and 54 can be explained by the intervention of 55 (n=2), which plays a pivotal role in the differentiation between intramolecular nucleophilic attack of the hydroxy group and reductive elimination of 54. Thus, the addition of base is believed to accelerate the conversion of 55 to the rhodate anion 56. This notation is supported by the fact that the introduction of a strong base such as DBU is advantageous for the selective formation of a lactone framework. 

Triphosphine, P3H5, has been identified as a product from the hydrolysis of CaaPj or Mg3P2 in acidic media by mass spectroscopy In addition, using mass spectroscopic analysis Baudler and her co-workers 436.437) able to identify the following higher phosphines formed during the hydrolysis or the disproportionation of diphosphine ... 

When the oxidation of a,a-dideuteriodiphenylmethane was interrupted after the absorption of 1.0 equivalent of oxygen, the product was found to be only benzhydrol and a trace of diphenylmethane (by GLPC). Mass spectroscopic analysis of the benzhydrol indicated 98.5% mono-deuterated material. 

An earlier set of experiments using icr techniques (Lieder and Brauman, 1974, 1975) also made use of the principle of collecting the neutrals during a certain amount of time followed by in situ mass spectroscopic analysis. Several examples were studied, among them cases which could give rise to more than one set of reaction products. Ethyl derivatives in particular can react according to two possible mechanisms, (25) and (26). The experiment... 

The former was detected by gas chromatography and mass spectroscopy. The lithium morpholinide powder was isolated by means of filtration. In order to be sure that there was no butyl-lithium or morpholine in the dry powder, G.C.-mass spectroscopic analysis of D O-quenched powder was performed. No deuterated butane or undeuterated morpholine was found. 

A simple method for preparing gold MPCs using dimercaptosuccinic acid (DMSA) as reducing and stabilizing agent has been reported. The core sizes are in the range 10 to 13 atoms (about 0.8nm), as observed in mass spectroscopic analysis [76]. 

To a soln of ester 92 (17 g, 66 mmol) in DMSO (28 mL) was added H20 (3.3 mL, 185 mmol) and NaCl (7.4 g, 128 mmol). The reaction flask was heated at 155 °C for 48 h. It was then cooled to 23 °C and the mixture was poured onto 1M HC1 (200 mL) and extracted with Et20 (3 x). The combined organic layers were washed with brine (3 x), dried (MgS04), filtered, and concentrated under reduced pressure. Mass spectroscopic analysis revealed the product to be predominately the ester 93 contaminated with a small amount of the acid 94. The crude material (11.5 g) was used without purification. 

All products were characterized by NMR, IR and mass spectroscopic analysis. Unfortunately, our efforts toward the synthesis of A-(terf-butylsulfinyl)imine under the optimum conditions using acetophenone was unsuccessful. 

Figure 38. Temperature-programmed decomposition (0.25 K s 1) of oxygen surface functional groups from a graphite powder. The simultaneous mass-spectroscopic analysis reveals the irreversible character of this experiment in which the substrate surface is removed during desorption of the adsorbate.

The infrared spectrum (v(CO) 2046 and 1969 cm 1) was again consistent with the presence of the desired polymer-bound complex, [Ir(CO)2I2]. ICP mass spectroscopic analysis of the metal loaded resins showed the metal contents to be 0.56-0.66 % (Rh) and 0.79-0.86 % (Ir) by weight. These values are in line with the observation that virtually all the metal complex is taken up from solution under the conditions of these loading experiments, and that 15-20% of the pyridinium sites are loaded with metal in the products. 

Mass spectroscopic analysis of proteins and peptide fragments has become an often-utilized technique over the past few years, and a number of microdevices have been reported for use with this analysis method. Though not yet used routinely in clinical analyses, detecting expression patterns and specific mutations in proteins may well be the best way to detect diseases and propose treatments specific for a given mutation. Transfer of this type of analysis to the clinical laboratory may await the development of microdevices for the sample preparation steps, which can interface directly with MS detectors. 

Most of HSQC peaks assigned to the N-terminal region disappear upon the formation of PYPm [33,34]. The loss of a-helical content is also observed by CD [35]. However the controversial conclusion was obtained by the fragmentation and H/D exchange mass spectroscopic analysis [36]. Therefore, detailed structural information about PYPm in solution is required to clarify the mechanism underlying the phototransduction. 

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